1. Technical Field
The embodiments described herein relate to a semiconductor memory device and, more particularly, to a test circuit for a semiconductor memory device.
2. Related Art
In general, after manufacturing, a semiconductor memory device is tested for normal operation by using a predetermined test apparatus to distinguish a good die and a bad die. In order to verify the semiconductor memory device, a test process is performed in which data provided from a tester is written in a memory cell and then the written data is read back for verification.
FIG. 1 is a schematic block diagram illustrating a relation between a conventional semiconductor memory device and a tester. Referring to FIG. 1, power lines are connected between the semiconductor memory device 1 and the tester 2 to provide external supply voltage VDD and ground voltage VSS such that write and read operations can be performed therebetween. However, power noise may occur in the external supply voltage VDD of the semiconductor memory device 1 due to undesired parastic resistance R, inductance L and capacitance C components of the power lines and power supply characteristics of the tester 2.
Thus, when the semiconductor memory device 1 does not operate, current consumption is small and the power supply is in a standby state. However, if the semiconductor memory device 1 starts a write or read operation, then current consumption is increased. Therefore, sudden fluctuation in a level of the external supply voltage VDD may be caused by the R, L and C components of the power lines and response characteristics of the tester 2. Since a power level from the tester 2 is unstable during the initial write or read operation of the semiconductor memory device 1, the test for writing and reading is performed after the power level has been stabilized, that is, after a write or read operation, which is not reflected in a test result, has been performed for a predetermined dummy cycle. For this reason, the testing time of a semiconductor memory device is increased.